package com.wc.AlgoOJ_homework.ALOJ模块测试Ⅱ.D_本质上升序列;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2024/5/16 14:55
 * @description http://43.138.190.70:8888/p/630?tid=663e2cd8d39d10926ed3fa74
 */
public class Main {
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 5010;
    static long[] f = new long[N];
    static Map<Character, Integer> map = new HashMap<>(128);
    static char[] s;

    public static void main(String[] args) {
        s = (" " + sc.next()).toCharArray();
        int n = s.length - 1;
        for (int i = 1; i <= n; i++) {
            int j = 1;
            f[i] = 1;
            for (; j < i; j++) {
                // only calculate lastIdx
                if (s[j] < s[i] && map.get(s[j]) == j) {
                    f[i] += f[j];
                }
            }
            map.put(s[i], j);
        }
        long res = 0;
        for (int i = 1; i <= n; i++) {
            if (map.get(s[i]) == i) res += f[i];
        }
        out.println(res);
        out.flush();
    }
}

class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}
